The effect of vacuum carbonization of waste maize stalk on the thermal resistance of polyester/maize stalk particulate composites has been investigated. Maize stalk was carbonized at a temperature of 1200oC to convert the biomass into biocarbon; then the carbonized maize stalk was used to reinforce polyester while the uncarbonized ones served as the control. The carbonized maize stalk particulates (CMSp) were added with different volume fractions into a polyester matrix at an interval of 2, 4, 6, 8, and 10% respectively. The thermal resistance of the composites was evaluated using the thermogravimetric (TGA) and differential thermal analysis (DTA). Results from the TGA/DTA examination showed that the resistance to thermal degradation of the carbonized polyester/maize stalk particulate composites is higher than the one that is not carbonized. Also, as the content of the carbonized maize stalk particulate increases, the thermal resistance of the composites increases. This result has indicated that the process of carbonization can enhance the degree of thermal resistance of the polyester/maize stalk particulate composites.